A form of vehicle seat which is typically used in tractors, trucks and the like has a base structure of a generally L-shaped configuration, with a horizontal portion which is fixed to the floor of the vehicle and a generally vertical portion extending upwardly from the horizontal portion. The seat has a seat plate which is arranged on the horizontal portion of the base structure and a backrest portion which is pivotably movably connected to the seat plate and which is mounted on the vertical portion of the base structure. At its underside the seat plate is provided with retaining members which are disposed at a spacing from each other, in the longitudinal direction of the seat, that is to say in the fore-and-aft direction. The horizontal portion of the base structure carries a stationary support mounting affording a further retaining member for latching engagement with one of the retaining members on the underside of the seat plate. It is found however that vehicle seats of that kind are of a more or less complicated design configuration, and that in turn has a detrimental effect on the manufacturing costs thereof.
A vehicle seat of that general design configuration is to be found in DE 39 29 432 Al. The seat has a spring assembly disposed between the backrest portion and the vertical portion of the L-shaped base structure. The spring assembly is disposed at that location because it is there that there is sufficient space for the spring assembly which, for reasons related to the springing action, may not be less than a given length.
In this general context also mention may be made of U.S. patent specification No 5 037 155 in which a vehicle seat has spring members disposed beneath a seat plate of the seat, but that seat does not have a generally L-shaped base structure nor does it involve a backrest which is pivotably connected to the seat plate.